Matlab Interactive Brokers Connection Response

Here's what I'm trying to achieve

Main Function

# Connect to Interactive Brokers TWS
# Verify that connection has been established
# If connection established, draw gui

end Main Function

Here's a basic code I have for this in Matlab

function main
  ib = ibtws('', 7496); %Connect
  while ~exist('ibBultInErrMsg', 'var') %Check for response
    pause(0.1)
  end
  drawGUI(); %If you've made it this far, then draw the gui
end

Here's the problem: the variable ibBuiltInErrMsg is only created once the main function is done running. (Matlab automatically creates this variable, and puts it in the same 'workspace' as the variable ib) I am trying to check within the Main Function if the variable ibBuiltInErrMsg does in fact exist. I am doing this as a form of connection verification since the object ib is constructed by Matlab in such a way that it does not provide a 'confirmation' flag for connection.

Essentially from my understanding is that Matlab does not block execution of the main thread to receive 'asynchronous' responses from external software.

Is there a workaround or will I have to use a more powerful language?

Thanks.